1. Field of the Invention
The present invention relates to a printing apparatus, a method of controlling the printing apparatus, and a storage medium.
2. Description of the Related Art
Image forming apparatuses that employ image forming processes such as an electrophotographic method and an electrostatic recording method are provided. In these apparatuses, a latent image is formed on a photosensitive member, and the latent image is developed with a developer to be visualized as a toner image. The toner image is transferred onto a recording material such as paper, and then, the recording material on which the toner image has been transferred is conveyed to pass through a nip portion formed with a fixing roller and a pressure roller provided in a fixing device. This process heats the toner image to fix it onto the recording material as an image.
In recent years, quick-start on-demand heating devices have been proposed as fixing devices, and have been put into practical use. In such an on-demand heating device, a rotatable endless heat-resistance thin flexible member is slidingly moved toward a heating member to apply the heat of the heating member to the recording material through the flexible member.
In such image forming apparatuses, to increase the productivity, first page out time (FPOT), which is the time necessary from the start of printing to the completion of discharge of a first recording material, is regarded as an important factor. There are many factors for determining the FPOT, and these factors can be roughly categorized into the following four items. The factors are, image information generation and rasterization time by an image information processing unit such as a video controller, rise time of a motor for rotating a scanner mirror in an exposure device, a length of a conveyance path from paper feed to conveyance and a conveying speed, and temperature rise time of a fixing device.
The temperature rise time of the fixing device is a time required for a heating member of a fixing heater provided therein to rise temperature up to a predetermined degree, which can be image-heatable, from the start of power supply to the fixing heater. The temperature rise time of the fixing device has a largest variation in the FPOT variation factors at the image forming apparatus side except an image rasterization time. The temperature rise time varies largely depending on a temperature of an image heating device at a start time of printing, an ambient temperature around the device, a power source voltage and so forth.
Steps of performing engine pre-processing by an engine controller at the printing start includes a pre-rotation control. In the pre-rotation control, in addition to heating processing of the fixing heater of the fixing device, control of the number of rotations of a polygonal mirror, high-pressure control, and transfer preparation are also performed. As a method of reducing the FPOT, a method for reducing the pre-rotation time including the fixing device rise time can be provided. The use of the above-mentioned on-demand heating devices is suitable for the purpose. Too much time reduction, however, causes an insufficient fixing temperature, and as a result, a fixing defect occurs. Consequently, simply reducing the pre-rotation time is not an appropriate method.
For the reduction of the FPOT, for example, Japanese Patent Application Laid-Open No. 2007-108297 proposes a method of changing the timing of recording material conveyance depending on a heating condition of a heating device, a power source voltage, and an ambient temperature. In this method, to ensure the fixation, as the number of disadvantageous conditions is small, the paper feed starts at an earlier stage to shorten the FPOT. On the other hand, as the number of disadvantageous conditions is large, the paper feed starting timing is delayed.
In Japanese Patent Application Laid-Open No. 2007-108297, to shorten the FPOT while reducing the fixing defect, temperature adjustment control is optimized depending on the ambient temperature. In the technique, however, print data is not considered, and to data of blank paper and a solid image, the same pre-rotation time is ensured. In other words, assuming worst conditions, the time enough to fix the solid image is always set. Consequently, it is not always a shortest time for reducing the FPOT while reducing the fixing defect.